The invention relates generally to in-tank fuel filters for installation on in-tank fuel pump assemblies and more specifically to an in-tank fuel filter having a retaining structure comprising a plurality of spring fingers arranged in an elongated circle. This configuration of fingers ensures ready mounting and retention of the filter assembly on the fuel pump assembly in spite of dimensional variation of filter mounting components on the fuel pump assembly.
The sophistication of modern vehicle fuel systems, particularly fuel injection systems, necessitates a supply of the cleanest possible fuel to such systems. Cleanest is currently defined as carrying contaminants such as foreign particulate matter having a size of less than about 100 microns. In order to satisfy the cleanliness requirements of such fuel systems, vehicle manufacturers have adopted two stage filtration schemes utilizing a first, relatively coarse fuel filter disposed in the fuel tank and a second finer, replaceable fuel filter in the engine compartment.
The in-tank fuel filter is generally assembled to the in-tank fuel pump assembly and this assembly is then mounted as a unit into the fuel tank.
Although the fuel filter will generally be retained upon the fuel pump assembly inlet simply by its position adjacent or against the bottom of the fuel tank once the assembly has been installed in the tank, maintaining the fuel filter in position after assembly and during transfer, storage and final installation into the fuel tank presents challenges. First of all, the fuel filter is preferably oriented in a specific radial direction on the fuel pump assembly inlet. Thus, a locating tab or other structure must be utilized. If such a locating tab is utilized, particularly as an integral feature of the fuel pump inlet fitting, experience has shown that providing a mating, properly configured structure for the positioning tab is problematic. Even very small dimensional variations in the sizes of such components may render assembly difficult or create a small gap through which unfiltered fuel may pass. Furthermore, the retaining structure must provide tight securement as the filter and fuel pump assembly will be handled several times before it is installed and protected in the fuel tank. Accordingly, the filter securement structure must be capable of withstanding repeated and relatively random and unpredictable dislodging forces.
Another problem common to in-tank filters is the tendency of the components, which are typically fabricated of a plastic such as nylon, polyester or acetal, to swell slightly upon prolonged exposure to hydrocarbon fuels, alternative fuels and their various additives. As noted above, since an in-tank fuel filter generally rests upon the fuel tank bottom, swelling of the outlet fitting will not result in dislodging of the fuel filter. However, since the fuel pump inlet fitting is typically fabricated of metal and is thus relatively dimensionally stable, such swelling will often create a gap between the filter fitting and the inlet fitting. If such swelling occurs, the effectiveness of the fuel filter will be seriously compromised.
Finally, it is desirable that the fuel filter securement structure not include small or loose parts that must be carefully handled and delicately assembled as this complicates and slows assembly of the fuel filter on the fuel pump assembly.
In view of the foregoing, it is apparent that improvements in the art of in-tank fuel filters and particularly those for installation on in-tank fuel pump assemblies which address these problems would be highly desirable.